Demanding off-road charging
When the rally drivers leave the bivouac in electric drive on the morning of each stage with a charged high-voltage battery, a highly complex control system begins. Only a few minutes before the start of the stage do the teams learn any details about the route at all when the roadbooks are handed out. The Audi RS Q e-tron with its innovative drive must always be prepared for all conditions in terms of distances, speeds, difficulty of the terrain and other factors. The engineers and electronic technicians have programmed algorithms to keep the State of Charge (SoC), i.e. the charge level, within defined ranges depending on the energy demand. Energy extraction and battery recharging are always in balance over defined distances. If, for example, a difficult dune passage with high driving resistance requires maximum energy for a short time, the state of charge drops within a controlled range. The reason: The drive power of the engine-generator units on the front and rear axles is limited to a maximum of 288 kW in total under the regulations. However, the energy converter can only provide a maximum charging power of 220 kW. In extreme cases, therefore, consumption is briefly higher than energy generation. “Something like this is possible for a limited time,” says Lukas Folie. “But over a longer distance, it always results in a zero-sum game: We then have to regulate the power consumption down so that the battery’s state of charge remains within a corridor. The absolute amount of energy available on board must be sufficient to cover the day’s leg.”